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Principles Related to Practical Chemistry

JEE Main 2024 (Online) 5th April Morning ShiftNumericalMedium📈 Topic in 41% papers+4
Ques. 1JEE Main 2024, 5 April (Morning Shift)

[figure] In a borax bead test under hot condition, a metal salt (one from the given) is heated at point B of the flame, resulted in green colour salt bead. The spin-only magnetic moment value of the salt is BM (Nearest integer) [Given atomic number of Cu = 29, Ni = 28, Mn = 25, Fe = 26]

Answer

6

Solution

Point B = inner (reducing) zone of the flame

Bead colours in the reducing flame: Fe → green; Cu → red (opaque); Ni → grey; Mn → colourless

⇒ green bead ⇒ the salt is an iron(III) salt

Fe3+ = [Ar]3d5 ⇒ n = 5 unpaired electrons

= n(n + 2) = 5 7 = 35 = 5.92 BM ≈ 6

Answer: 6

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Ques. 2JEE Main 2024, 5 April (Evening Shift)

While preparing crystals of Mohr's salt, dil H2SO4 is added to a mixture of ferrous sulphate and ammonium sulphate, before dissolving this mixture in water, dil H2SO4 is added here to :

  1. prevent the hydrolysis of ferrous sulphate
  2. prevent the hydrolysis of ammonium sulphate
  3. increase the rate of formation of crystals
  4. make the medium strongly acidic
Ques. 3JEE Main 2024, 5 April (Evening Shift)

Using the given figure, the ratio of Rf values of sample A and sample C is x 10-2. Value of x is . [figure]

Ques. 4JEE Main 2024, 4 April (Morning Shift)

In the precipitation of the iron group (III) in qualitative analysis, ammonium chloride is added before adding ammonium hydroxide to :

  1. decrease concentration of -OH ions
  2. increase concentration of Cl- ions
  3. prevent interference by phosphate ions
  4. increase concentration of NH4+ ions
Ques. 5JEE Main 2024, 4 April (Morning Shift)

Which of the following nitrogen containing compound does not give Lassaigne's test ?

  1. Glycine
  2. Phenyl hydrazine
  3. Urea
  4. Hydrazine
Ques. 6JEE Main 2024, 4 April (Evening Shift)

When MnO2 and H2SO4 are added to a salt (A), a greenish yellow gas is liberated. The salt (A) is :

  1. NH4Cl
  2. CaI2
  3. KNO3
  4. NaBr
Ques. 7JEE Main 2024, 4 April (Evening Shift)

The adsorbent used in adsorption chromatography is/are - Choose the most appropriate answer from the options given below :

  1. C and D only
  2. A only
  3. B only
  4. A and B only
Ques. 8JEE Main 2024, 1 February (Morning Shift)

In Kjeldahl's method for estimation of nitrogen, CuSO4 acts as :

  1. catalytic agent
  2. hydrolysis agent
  3. reducing agent
  4. oxidising agent
Ques. 9JEE Main 2024, 1 February (Morning Shift)

Given below are two statements : In the light of the above statements, choose the most appropriate answer from the options given below :

  1. Both Statement I and Statement II are correct
  2. Statement I is incorrect but Statement II is correct
  3. Both Statement I and Statement II are incorrect
  4. Statement I is correct but Statement II is incorrect
Ques. 10JEE Main 2024, 1 February (Morning Shift)

The number of white coloured salts, among the following is (a) SrSO4 (b) Mg(NH4)PO4 (c) BaCrO4 (d) Mn(OH)2 (e) PbSO4 (f) PbCrO4 (g) AgBr (h) PbI2 (i) CaC2O4 (j) [Fe(OH)2(CH3COO)]

Ques. 11JEE Main 2024, 1 February (Evening Shift)

Given below are two statements : In the light of the above statements, choose the most appropriate answer from the options given below :

  1. Statement I is false but Statement II is true
  2. Both Statement I and Statement II are true
  3. Statement I is true but Statement II is false
  4. Both Statement I and Statement II are false

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